1. Field of the Invention
The present invention relates to a vehicle provided with a yaw rate sensor and an apparatus for detecting an anomaly of a yaw rate sensor used in this vehicle.
2. Related Background Art
Vehicle control such as rear wheel steering control or vehicle posture control often utilizes a yaw rate obtained by the yaw rate sensor, as one of control parameters. In such control, if the yaw rate sensor is abnormal and if it is neglected, false vehicle control will result naturally. It is, therefore, necessary to monitor the status of the yaw rate sensor and to perform some operation to handle an anomaly if any.
As an apparatus of this type for monitoring the status of the yaw rate sensor there is an apparatus for detecting an anomaly of the yaw rate sensor.
Japanese Laid-open Patent Application No. Hei 4-135980 discloses the invention of four wheel steering apparatus, in which there is the description about the anomaly detecting apparatus for yaw rate sensor arranged to make a decision that the yaw rate sensor is abnormal, when a change rate of yaw rate exceeds a predetermined value.
In this conventional anomaly detecting apparatus for yaw rate sensor, however, road surface conditions are not taken into consideration in the decision on the anomaly of yaw rate sensor, and it is presumed that a threshold value for the decision on the anomaly is set on the premise that the vehicle runs under ordinary road surface conditions.
During running on a bad road, however, vibration of vehicle is superimposed on values of yaw rate detected by the yaw rate sensor, so that change rates of yaw rate sometimes become large values that would never appear during running on a good road.
When the threshold value for the decision on the anomaly is set on the premise that the vehicle runs on a good road, it is highly probable that an erroneous decision of anomaly is made during running on a bad road.